Roots and Stems

Functions of Roots  Anchor the plant  Absorb water and nutrients from the soil and transports them to the stems and leaves  Store food for the plant  Help prevent soil erosion

Parts of a Root System Primary Roots  Grow from the hypocotyl part of the seed embryo Root Hairs  Hair-like extensions that make their way through the openings between soil particles  Water and nutrients enter the root hairs and travel up the secondary and primary roots to the stems and leaves Secondary Roots  Branch off of the primary root

Parts of a Root System Primary Root Secondary Roots Root Hairs

Taproot One large root with smaller secondary roots attached to it They penetrate deep into the soil Examples: carrot, dandelion, oak trees

Fleshy Taproot  Acts as a food storage area of the plant  Examples: carrots, turnips, beets

Fibrous Root  No recognizable primary root  Lots of fine, thread-like roots of the same size  Originate at the base of the stem  Spread near the surface of the soil  Examples: grasses, shrubs WHICH ONE?

Balance Between Roots and Stems  Roots supply water and minerals to shoots, while shoots supply food to roots.  Hormones normally balance growth of roots and shoots.  Roots produce cytokinin, which travels to shoots and promotes bud growth.  Shoots produce auxin, which travels to roots and promotes root growth.

Functions of Stems  Transports materials up and down the plant through the vascular system Consists of xylem and phloem tissue Young stems have vascular bundles, which consist of both xylem and phloem Woody stems have a vascular cylinder in which the outer portion is the phloem and the inner portion is the xylem

Xylem Tissue  Moves water and nutrients UPward from the roots to the stems and leaves Phloem Tissue  Moves water and nutrients DOWNward from the stems and leaves to the roots

Other Functions of Stems  Provide physical support for leaves, fruit and flowers  Store food (Ex. Onions, garlic, potatoes)  Green stems have chlorophyll in them and conduct minor photosynthesis  Capable of reproduction  Help establish tendrils which aid climbing plants

Types of Stems  Herbaceous – soft tissue that bends (ex: houseplants)  Woody – brittle, non-bendable, bark-like tissue (ex: trees, shrubs)